The proposed research will determine the mechanism by which a primary chemoreceptor neuron on the antenna of the yellow fever mosquito, Aedes aegypti, makes a qualitative discrimination between behaviorally significant chemical stimuli, i.e., attractant, repellent, etc., and how it quantifies and presents this information to the mosquito's central nervous system for processing and initiation of an appropriate behavioral response. Extracellular recordings of nerve spike potentials from the primary chemoreceptor cells will provide a basis for understanding the sensory-behavioral mechanism of the mosquito that are essential for its eventual regulation and control.